Featured Image Caption: Coral reef nurseries have been used to restore coral reefs for the past five decades, but survival rates after planting aren’t always the best. So, what can be done to make reefs more resilient while also being more effective when it comes to restoration? (Image Source: “Loaded coral tree” by FWC Fish and Wildlife Research Institute licensed under CC BY-NC-ND 2.0).
Reference: Shaver, E., McLeod, E., Hein, M., Palumbi, S., Quigley, K., & Vardi, T. et al. (2022). A roadmap to integrating resilience into the practice of coral reef restoration. Global Change Biology. https://doi.org/10.1111/gcb.16212
Coral reefs are some of the most diverse and threatened ecosystems on Earth. Corals represent 25% of all marine species, but they only cover 1% of the ocean floor. They serve as food and shelter for many marine species and therefore have a high ecological value. Apart from this, corals also bring many benefits for us, as they absorb wave energy and help reduce coastal erosion. They buffer the shores from damage caused by storms, hurricanes, and other cyclones, as well as, to some extent, the energy of tsunamis. In this way, they protect both the ecosystems located between the reefs and the coasts, such as lagoons that host beneficial seagrass meadows, for example, and human settlements located by the sea.
A Wave of Threats to Coral Reefs
Three factors exert strong pressures on coral reef ecosystems: coral bleaching, decreasing herbivory rates, and human activities that lead to pollution, sedimentation, and excess nutrient inputs with a consequent increase in algal biomass that smother corals.
Coral bleaching linked to climate change is the biggest problem coral reefs are facing worldwide. Coral bleaching is a phenomenon that occurs when increasing temperatures and acidity lead to the expulsion of the coral’s single-celled symbionts, which provide more than 95% of the coral’s metabolic requirements. When the symbiont leaves the coral colony, it is extremely hard for them to recover.
Then factor in other threats—like the decrease in herbivores and increase in pollution that bring in excess nutrients, which both lead to algal accumulation on corals, essentially suffocating them—and it isn’t hard to believe that coral reefs are struggling all over the world.
What Is Coral Reef Restoration?
Restoration is the process by which we assist the recovery of an ecosystem that has been damaged or degraded. Therefore, all actions taken in order to conserve and help recover coral reef ecosystems are considered to be coral reef restoration. The most common of these efforts are coral reef nurseries, which allow coral fragments to grow in a more-or-less controlled environment until they are big enough to survive in the reef on their own. Sadly, these actions aren’t as effective as expected. That is why scientists have been looking at ways to give these corals a better chance, in hopes that they will endure the continuously and rapidly changing conditions of oceans.
Resiliency Prevails When All Else Fails
Elizabeth Shaver, from The Nature Conservancy, and a group of scientists from all around the world, ranging from the Americas all the way to Oceania, decided to review different studies addressing coral reef resilience and present concrete suggestions on what has worked and what hasn’t.
When it comes to designing coral reef restoration projects, the researchers suggest that projects should be designed to integrate adaptation to climate change and utilize techniques that foster coral resilience and recovery. They also emphasize the importance of including and engaging local communities to promote awareness.
They recommend that project managers prioritize coral colonies that are sourced from at least 10 colonies spaced five meters apart and come from a variety of reef habitats and conditions. They further suggest that these coral colonies for restoration represent a diversity of growth forms and functions and come from thermal- and disease-resistant genotypes and species.
When it comes to selecting a restoration site, they highlight that sites that represent a variety of reef habitats and conditions, have high diversity and redundancy of herbivores, are less likely to experience environmental change, and supply coral and fish larvae to other areas should be prioritized.
Finally, the scientists remind policymakers and decision-makers that coral reef restoration is not enough. Researchers should conduct coral reef restoration as part of an effective management plan and alongside the protection and restoration of other marine habitats. In a similar fashion, we should strive to reduce the threats corals face, may that be through resilient breeding or protecting herbivore species. They also emphasized that project managers should be focusing on ecological processes and species that support corals, not only on restoring corals for the sake of restoring corals, with no notion of if they’ll survive or not.
We live in a world that’s highly focused on what’s above water, without taking into consideration that our oceans produce around 50 to 80% of the oxygen we breathe. It is not too late. We can still help these ecosystems recover. It is time to start thinking about more than just coral reef restoration, but about how to give these coral reefs a fighting chance in the long run.